1. Field of the Invention
The present invention relates to a porous resin stamp, which can repeatedly make a seal impression without supplying ink for a long period of time such as by soaking the stamp in ink before use.
2. Description of the Related Art
There is a porous resin stamp known simply as a stamp, which can repeatedly make a seal impression without supplying ink each time by beforehand soaking ink into the stamp. A porous resin stamp is comprised of porous resin having open cells through which ink is supplied onto the stamp surface, thus, it is possible to repeatedly make a seal impression.
As for a method for producing such porous resin stamps, a stamp manufacturing process by a making a thermal head, a stamp manufacturing processing by the use of a flashing light, and a thermal transfer method and such are known. This stamp manufacturing processing by a flashing light is a method to irradiate light such as infrared light toward a surface of a porous resin body so that heating material is made to be negatives, i.e., complements to desired letters, designs, patterns and such by generating heat, and to form ink inexuding portion and ink exuding portion by melting the surface layer of the porous resin body.
As a concrete example of the stamp manufacturing processing by a flashing light, is a porous resin stamp wherein open cells are filled by melting a surface of the porous resin body by making and locating a black pigment to generate heat with an irradiating light directed onto the surface of the porous resin body, which is layered with a layer beforehand combined with predetermined amount of black pigment or with a layer of which surface comprised of black pigment, is disclosed in a publication of Japan patent application Tokuganhei 9-314972.
However, the above mentioned existing porous resin stamp has the following problems. The porous resin stamp disclosed in the publication of Japan patent application Tokuganhei 9-314972 was inferior in reproducibility, particularly of thin lines and spots, because this porous resin stamp only comprised black pigment as a heating material, of which heat conductivity was high, and thus, irradiated part and the surrounding porous resin body became melted when melting the porous resin body with generated heat from the heating of the heating material by irradiating light.
Also, in a case of a porous resin stamp soaked only in black pigment, the porous resin stamp became only one color, black. For example, in a case of soaking the stamp in black ink which is used most frequently, it became difficult to discern the ink and the desired letters, designs, patterns and such formed on the stamp surface, and consequently, it was difficult to distinguish the top and bottom and the right and left of the stamp surface. Further, it was difficult to find a stain impression adhered, thus, it was inconvenient to use.
Moreover, since the porous resin body and an original being directly in contact were irradiated with light when producing the porous resin stamp, there might be some cases where the melted porous resin body and the heating material could have beforehand combined with the porous resin body and could have become adhered to the original. Therefore, the problem was that the original itself could not be re-used directly when producing the same stamp.